Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$116.44	5.276%	$122.5834	$122.58	$122.60	$122.60
Purchase #2	$90.93	9.489%	$99.5583	$99.56	$99.55	$99.60
Purchase #3	$206.42	3.606%	$213.8635	$213.86	$213.85	$213.90
Purchase #4	$88.61	12.118%	$99.3478	$99.35	$99.35	$99.30
Purchase #5	$72.37	5.158%	$76.1028	$76.10	$76.10	$76.10
Purchase #6	$82.44	12.336%	$92.6098	$92.61	$92.60	$92.60
Purchase #7	$56.93	7.653%	$61.2869	$61.29	$61.30	$61.30
7 purchase totals =	$714.14		$765.3525	$765.35	$765.35	$765.40